1. Field of the Invention
The present invention relates to a data transmission apparatus and is suitably applied to a portable compact disc player which can be controlled by a wireless remote commander.
2. Background of the Invention
Heretofore, in the portable type compact disc player, there have been some miniaturized devices which can be driven by a battery.
More specifically, by miniaturizing the whole shape and driving the apparatus with a battery, this type of compact disc player can be easily portable and the user can appreciate music at the desired place.
Hereupon, in this type of compact disc player, if the compact disc player body and the control unit are formed separated and audio signal can be reproduced at the compact disc player body and simultaneously, the reproduced audio signal can be wireless transmitted to the control unit, the user can appreciate music in a state where the compact disc player body is put in a bag and the usability of this type of compact disc player can be improved.
If the wireless remote commander function would be operated in the control unit, the operation of a compact disc player body can be controlled in a state where the compact disc player body is put in a bag.
Furthermore, if a display unit is formed in this control unit and the operation of the compact disc player body can be confirmed through this display unit, the usability can be further improved.
Therefore, it is necessary that the compact disc player body wireless transmits audio signals and display data to the control unit, and also the control unit wireless transmits the control data for switching the operation to the compact disc player body.
In the portable compact disc player of this type, it is also necessary to downsize the shape of the control unit.
Furthermore, it is necessary for the control Unit to lower the operating voltage and to further decrease the consumption of the power source.
However, if the operating voltage is lowered, it becomes essential to decrease the operating speed in the control unit, and after all, it takes time for receiving process of the display data outputted from the compact disc player body.
On the other hand, it is necessary that in this control unit, the operation of the operation key is detected at a predetermined cycle, and depending upon the detected result thereof, the control data must be outputted to the compact disc player body.
Thus, if the operating voltage of the control unit is lowered, the key scanning cycle of the operation key becomes longer for the time required for receiving process of the display data, and accordingly the usability becomes worse.
Because of the above-mentioned problem, even if the operation key in the control units operated by the user, the responding speed of the compact disc player body deteriorates.
As one of the methods to solve the above problem, the method for performing the process of outputting the control data by key scanning in synchronism with the process of receiving the display data at two processing systems can be considered. However, if such a case would be done, construction of the control unit becomes complicated and also the consumption of power increases.